Conveyor systems, which can include a plurality of conveyors arranged in series, are commonly used to transport bulk material, e.g., coal, or rocks and/or stones, from an extraction site, e.g., a mine or quarry, to a discharge location where the bulk material can be loaded onto vehicles for distribution. Known conveyor systems include those having an upstream conveyor positioned near the extraction site. The upstream conveyor includes an impact load bed, which defines an impact load zone, and a driven pulley commonly referred to as a head pulley. Rotation of the head pulley causes an endless conveyor belt that is coupled with the head pulley to travel in a loop, from a rotatable tail pulley through the impact load zone to the head pulley, and back to the tail pulley.
The impact load bed includes a plurality of impact idlers, each having a plurality of rollers, and/or a plurality of impact saddles, which are arranged along the length of the impact load zone. The impact idlers and/or impact saddles are configured such that they cooperate to define a generally V-shaped trough. The conveyor belt is positioned within the trough and slides across the rollers of the idlers and/or an upper surface of segments of each of the impact saddles, which are constructed from a material having a relatively low coefficient of friction, during operation of the upstream conveyor.
The conveyor belt is substantially flat, or planar, as it leaves the tail pulley. The conveyor belt transitions from this substantially flat shape to the generally V-shape of the trough, as it travels through a transition zone that extends between the tail pulley and the impact load zone. Some known conveyors are configured such that an uppermost portion of the tail pulley, from which the conveyor belt leaves, is higher than a lowest portion of the trough. Known conveyors of this type are referred to as having a partial trough transition, and the change in shape of the conveyor belt is at least partially a result of bulk material dropping onto the conveyor belt, and forcing the conveyor belt downward into the trough, as the conveyor belt travels through the impact load zone. Various parameters, such as tension in the conveyor belt, and the difference in height between the uppermost portion of the tail pulley and the lowest portion of the trough, can cause the conveyor belt to spring upward, changing the position of the conveyor belt relative to the trough.
Some known conveyors having a partial trough transition are associated with a chute. The chute is configured to permit bulk material to be dropped onto the conveyor belt, but otherwise encloses the conveyor belt. The chute may include side skirt boards, and flexible seals attached to the lower ends of the side skirt boards. The flexible seals contact the conveyor belt to prevent, or at least substantially prevent, dust or fine particles of the bulk material escaping into the surrounding atmosphere, which can be the interior of a mine, to facilitate compliance with established environmental and/or mine safety regulations. In some instances, vertical movement of the conveyor belt during operation of the conveyor degrades the side skirt board seals, resulting in dust or fine particles of the bulk material escaping into the surrounding atmosphere.
Some known conveyors having a partial trough transition include side skirt boards that are not associated with a chute, and flexible seals that are attached to the lower ends of the side skirt boards and in contact with the conveyor belt. In some instances, vertical movement of the conveyor belt during operation of the conveyor degrades these side skirt board seals resulting in pieces of the bulk material that is being conveyed to become trapped, or lodged, under the side skirt board seals. This can cause significant damage to the conveyor belt as it moves over the trapped material.
Some conventional conveyors are configured such that an uppermost portion of the tail pulley is in the same plane as the lowermost portion of the trough. Known conveyors of this type are referred to as having a full trough transition, and are not as susceptible to vertical movement of the conveyor belt as conveyors having a partial trough transition. However, a conveyor operator can incur increased costs associated with the use of conveyors having a full trough transition, for example, but not limited to, the cost associated with the increased length of a typical conventional conveyor having a full trough transition as compared to the length of a typical conventional conveyor having a partial trough transition.